Function _gr_poly_compose_mod 

pub unsafe extern "C" fn _gr_poly_compose_mod(
    res: gr_ptr,
    poly1: gr_srcptr,
    len1: slong,
    poly2: gr_srcptr,
    poly3: gr_srcptr,
    len3: slong,
    ctx: *mut gr_ctx_struct,
) -> c_int